Process for simultaneous bleaching and neutralization of alpha-sulfofatty acid esters

Abstract

For the production of solid, substantially anhydrous alkali metal salts of α-sulfofatty acid alkyl esters containing from 8 to 22 carbon atoms in the fatty acid chain and from 1 to 6 carbon atoms in the ester alkyl radical, solid or molten α-sulfofatty acid alkyl esters are simltaneously mixed with an aqueous solution of hydrogen peroxide or an H 2 O 2 -yielding compound and with solid alkali metal carbonate at a temperature of from 20° to 80° C. optionally in the presence of aqueous alkali metal hydroxide, the ratio by weight of ester of H 2 O 2 being from 1:0.01 to 1:0.06 and the molar ratio of ester to alkali metal carbonate being in the range of from 1:0.5 to 1:0.75, the foam formed through the release of CO 2 is mechanically destroyed under a pressure of from 0.2 to 1.0 bar and at a temperature of from 50° to 70° C., and the product formed is residually degassed and residually dehydrated under a pressure of from 15 to 50 mbar and a temperature of from 50° to 80° C.

We claim: 
     
       1. A process for the production of solid, substantially anhydrous alkali metal salts of α-sulfofatty acid alkyl esters by oxidative bleaching and neutralization of α-sulfofatty acid alkyl esters containing from 8 to 22 carbon atoms in the fatty acid chain and from 1 to 6 carbon atoms in the ester alkyl radical, comprising the steps of (a) simultaneously mixing together solid or molten α-sulfofatty acid alkyl esters, an aqueous solution of hydrogen peroxide or an H 2  O 2  - yielding compound, and solid alkali metal carbonate at a temperature of from about 20 to about 80° C., wherein the ratio by weight of ester to H 2  O 2  is from about 1:0.01 to about 1:0.06 and the molar ratio of ester to alkali metal carbonate is in the range of from about 1:0.5 to about 1:0.75,   (b) destroying the foam formed through the release of CO 2  under a pressure of from about 0.2 to about 1.0 bar, and at a temperature of from about 50° to about 70° C., and   (c) degassing and dehydrating the product formed under a pressure of from about 15 to about 100 mbar and at a temperature of from about 50° to about 80° C.   
     
     
       2. The process of claim 1 wherein step (a) is carried out in a stirring vessel, a kneader, or a screw mixer. 
     
     
       3. The process of claim 1 wherein molten α-sulfofatty acid alkyl esters are used in step (a). 
     
     
       4. The process of claim 1 wherein α-sulfofatty acid alkyl esters containing from 12 to 18 carbon atoms in the fatty acid chain are used in step (a). 
     
     
       5. The process of claim 1 wherein the α-sulfofatty acid alkyl esters contain from 1 to 3 carbon atoms in the alkyl ester radical. 
     
     
       6. The process of claim 4 wherein the α-sulfofatty acid alkyl esters contain from 1 to 3 carbon atoms in the alkyl ester radical. 
     
     
       7. The process of claim 1 wherein the α-sulfofatty acid alkyl ester is a methyl ester. 
     
     
       8. The process of claim 1 wherein in step (b) the foam is destroyed by mechanical means. 
     
     
       9. The process of claim 1 wherein step (c) is carried out with mechanical agitation. 
     
     
       10. The process of claim 1 wherein in step (a) an about 30 to an about 70% by weight aqueous solution of hydrogen peroxide in a ratio by weight of ester to H 2  O 2  of from about 1:0.03 to about 1:0.05 is employed. 
     
     
       11. The process of claim 1 wherein in step (a) an alkali metal hydroxide is present and wherein the molar ratio of ester to alkali metal carbonate is from about 1:0.5 to about 1:0.525 and the molar ratio of ester to alkali metal hydroxide is from about 1:0.03 to about 1:0.08. 
     
     
       12. The process of claim 1 wherein in step (a) the alkali metal carbonate is sodium carbonate. 
     
     
       13. The process of claim 11 wherein the alkali metal hydroxide is sodium hydroxide. 
     
     
       14. The process of claim 1 wherein step (a) is carried out at a temperature of from about 50° to about 80° C. 
     
     
       15. The process of claim 1 wherein step (b) is carried out a under a pressure of from about 0.2 to about 0.5 bar. 
     
     
       16. The process of claim 1 wherein in step (a) an aqueous solution of hydrogen peroxide, and sodium carbonate are employed at a temperature of from about 50° to about 80° C., and step (b) is carried out at a pressure of from about 0.2 to about 0.5 bar. 
     
     
       17. The process of claim 1 wherein step (a) is carried out in the presence of an aqueous alkali metal hydroxide.